Production of chromium compounds and alkalies.



' No. 728,778. PATENTED MAY 19, 1903..

H. SPEGKETER.

PRODUCTION OF OHROMIUM COMPOUNDS AND ALKALIES.

APPLICATION FILED JULY 1, 1901.

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UNIT D STATES Patented May 19,1903.

PATENT. CFFICE.

HEINRICH sPECKETER, OF GRIESHEIM-CN-THE-MAIN, GERMANY, ASSIGNOR TO CHEMIsCHE FABRIK GRIESHEIM ELECTRON, or FRANKFORT-ON-THE- MAIN, GERMANY, A FIRM.

PRODUCTION OF CHROMIUM COMPOUNDS AND ALKALIES.

SPECIFICATION forming part of Letters Patent No. 728,778, dated May 19, 1903.

Application filed July 1, 190]- Serial No.' 66,74=7. (No specimens-l To all whom, it may concern.-

Be it known that I, HEINRICH SPECKETER, a subject of the Emperor of Germany, and a resident of 1 Bahnstrasse, Griesheim-on-the- Main, near Frankfort-on-the-Main,Germany, have invented certain new and useful Improvements in the Production of Chromium Compounds and Alkalies, of which the following is a specification.

The principal object of this invention is to provide a process for economically and on a commercial scale producing chromium compounds and alkalies. The said process consists, essentially, in subjecting to electrolysis the solution of any alkali-metal salt or of mixture of alkali-metal salts and using an anode of chromium or an alloy thereof or by using salts of chromium. as an electrolyte with an insoluble anode, the anode electrolyte being separated from the cathode electrolyte by a diaphragm or other equivalent means preventing the said liquid becoming mixed, while hydroxids or carbonates are added to the electrolyte for the purpose of precipitating the alkali-metal salt with the chromium and neutralizing the free acid which is formed along'with the chromic acid. In the accompanying drawings there is representedaconventional form of battery which may be used in carrying out the process.

In the drawings, Figure l is a vertical section, and Fig. 2 is a horizontal section.

0 represents the anode, b the cathode, and c d the diaphragms.

This invention can be carried out as follows: The electrolyte consists, for instance, of a solution of sodium sulfate. The anode is of ferrochrominm, such as is obtained in the reduction of chrome-iron by carbon. The anode is separated from the cathode by a diaphragm. Calcium carbonate or caustic lime is added to the anode electrolyte. When an electric current is passed through the electrolyte, the following reactions take place: A soda-lye is produced in the cathode-compartment in accordance with the following equation:

(1.) Na+H O=NaoH+H.

In the anode-compartment free chromic acid, free sulfuric acid, and ferric sulfate are formed, but undergo the following transformations in the electrolyte:

(4..) H Ci-O +H SO,+2Ca(OH) CaCrO +CaSO +2H O. (5.) Fe (SO +3Ca(O-H) 2 4 a Fe (OH) +3CaSO,. (6.) CaCrO,+Na SO =Na CrO +CaSO The impurities pass into the precipitate and are separated by filtration, while the sodium chromate remains in the solution,which is evaporated to dryness or transformed by means of sulfuric acid into sodium bichro one-half to three-volts, and the amperage is from one and one-half to two amperes per square decimeter. When the concentration of the chromic acid reaches about one hundred grams per liter, the solution is emptied,

the iron hydroxid and gypsum separated by filtration,-and the solution evaporated to crystallize the sodium chroma te. The cathodelye is likewise evaporated when its concentration amounts to fifty or sixty grams of sodalye per liter, and the precipitated sodium sulfate can be used-again in the process.

It is known that chromium and chromium alloys used as anode'in a solution of alkalimetal salts pass into the solution as chromic acid. It is also known that the electrolysis of alkalimetal salts produces hydroxid at the cathode. If this process were carriedout without the use of a'diaphragm or other device preventing the intermingliug of the anode and cathode electrolytes, the process would be unprofitable.

It is, however, rendered profitable by co tn biuing both the anode and cathode process in the hereinbefore-described mannerand obtaining from salts of low value, such as sodium chlorid or sodium sulfate, a valuable soda-lye, as well as chr0- mates, which final products have all a good marketable value.

The special feature of the present processcousists, therefore, in the simultaneous and combined electrolysis of chromium compounds and alkali-metal salts,whereby a valuable alkali and chromic acid are simultaneously obtained. Such a combined extraction.

of alkali and chromic acid from initial products of low value is neither described in the special literature 'nor has it hitherto, as far as is known, ever been carried out.

It should be further remarked that two diaphragms may be used in the aforesaid process and the free acid neutralized with lime or the like in the space between these two diaphragms. The neutralization of the anodelye and the precipitation of the iron are then is also sodium sulfate, to which, for instance,

lime or calcium carbonate is added. The

cathode is of iron and the anode of lead.

When the chromium sulfate is oxidized to chromic acid, which maybe seen from the color, the solution is raised to the ebullitionfrom 150 to 160 cen'tigrade.

p0iut'-120 to centigrade. The iron sulfate crystallizes out and is separated by filtration. To separate the chromic acid, the filtrate is boiled to a temperature of about The 'chromic acid is precipitated and separated by filtration. The filtrate contains still small quantities of chromic acid and of unoxidized chromium sulfate in the form of chromium sulfuric acid and can be used again to dissolve ferrochromium. It is also possible by evaporating the original solution to from to centigrade to precipitate both the. iron sulfate and the chromic acid and extract the chromic' acid from the mixture by means of water or sulfuric acid. The ferric sulfate is washed out with water or sulfuric acid in order to remove the chromic acid included therein. I

Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed, I declare that what I claim is 1. The process, substantially as herein described, of producing chromium compounds and alkalies, which consists in electrolyzing solutions of the salts ofthe alkalies with an anode containing chromium, while preventing the intermingling of the anode and cathode electrolytes and adding to the anode electrolyte a neutralizing agent.

2. The process, substantially as herein described, of producing chromium compounds and alkalies, which consists in electrolyziug solutions of the salts of the alkalies with an anode containing chromium, while preventing the intermingling of the anode and cathode electrodes and adding to the anode electrode -a hydroxid.

In testimony whereof I have signed my name to this. specification in the presence of. two subscribing witnesses.

HEINRICH SPECKETER.

Witnesses:

FRANZ HASSLACHER, MICHAEL VOLK. 

